The Journal of Recreational Mathematics published this remarkable magic square, composed by “a puzzlist who at the time was a prison inmate.”

The large 13 × 13 square is magic — that is, each row and column adds to the same sum — but so is each successive nested square, from 11 × 11 down to 3 × 3.

The magic constant of each square is 10,874 smaller than the last.

And every cell is prime.